ABSTRACT: Ocean acidification, the reduction in pH and calcium carbonate saturation states of seawater, is likely to exhibit its most immediate effects on cold-water corals in deep waters with the shoaling of the aragonite saturation horizon. However, empirical data describing the carbonate chemistry at cold-water coral reefs are very rare. Regions of the upper slope of the Northern Gulf of Mexico harbor several deep-water reefs structured by the scleractinian Lophelia pertusa. We collected discreet water samples at a range of depths in the Gulf of Mexico, including eight Lophelia reefs, and measured total alkalinity and pH to calculate the aragonite saturation state (&ohm;arag). The deep waters of the Gulf of Mexico (> 300 m depth) were at aragonite saturation states between 0.98 and 1.69. L. pertusa was present at sites with &ohm;arag between 1.25 and 1.69, and carbonate ion concentrations between 92 and 123 µmol kg−1. These data provide a critical baseline for detecting future changes in carbonate chemistry in the water column (i.e., aragonite saturation horizon shoaling), as well as at the sites of well-developed cold-water coral structures threatened by ongoing ocean acidification.

Article Links

Please Note

Articles in L&O appear in PDF format. Open access articles may be freely downloaded by anyone. Other articles are available for download to subscribers only, or may be purchased for $10 per article. All L&O articles are moved into Open Access after three years.